The present invention relates to a method and an apparatus for deoxygenating a food product and packing it. The apparatus and method according to the invention are particularly suitable for deoxygenating and flow-wrapping oxygen sensitive products such as dough products, folded food products or products of complex structure enveloping air. The invention also relates to a deoxygenated food package.
For the storage of food products sealed in packages, the level of oxygen in the package may be determinative for the life of the product. This is especially the case for oxygen sensitive products such as fresh or uncooked dough products, meat products etc. Hence, the release of oxygen in the package decreases the life of the product. Such a release of oxygen can often be observed by an inflation of the package.
To decrease the oxygen within a package it is known to gas flush the package containing the product before sealing it. When packing pulverized products, gas flushing of the product immediately prior to the packing is known. In this way, the atmosphere in the head space above and around the product is replaced with a suitable gas such as nitrogen or carbon dioxide.
This kind of replacement of the atmosphere in a food package containing a product does, however, suffer from the drawback that oxygen in the product will be developed a few hours after packing of the product with the undesirable effect of the oxygen as discussed above.
This problem is substantial when packing dough based products as a result of the level of oxygen content in the product and release thereof. Food products of complicated structure or folded products encapsulating pockets of air give also additional oxygen in the package.
Prior art packing machines aim to reduce the level of oxygen in the package by subjecting the package containing the product to a vacuum possibly followed by subsequently flushing the package and product with a suitable gas. For example, evacuating the atmosphere from pouches containing products can take place in a Flow-wrap machine before sealing the pouches. In a Flow-wrap machine, pouches are shaped around a mandrel from one reel of foil and welded into pouches. Due to the evacuation of the atmosphere, the pouch is sucked close to the product and creates a "vacuum" packing of the product. The evacuation of each package reduces the packing capacity of the machine considerably and it is therefore generally only used for bigger items e.g. steaks. This packing method has therefore been considered unsuitable for many purposes due to the relatively low capacity of a maximum of 8 to 10 packing cycles/min.
The evacuating principle is also employed in thermoshaping packing machines such as a Multivac.TM. in which trays are formed from a lower plastic foil. The trays are filled with food products and then the atmosphere around the tray with the product therein is evacuated. Immediately following the evacuation, the tray and food product are flushed by gas and an upper plastic foil is applied to seal off the tray. The Multivac.TM. type of packing requires large amounts of packing material. For example, the thickness of the packing base material of the Multivac.TM. is about 500 .mu.m while the foil used for the flow wrap packing is about 80 .mu.m.